1. Field of the Invention
The present invention generally relates to an electrophotographic apparatus using the so-called Carlson process in which an image on a document surface is copied onto an ordinary paper, and more particularly to an electrophotographic apparatus in which a position on a document surface is selected and the intensity of exposure to a photosensitive body is controlled in accordance with the selected position on the document surface so that it is possible to perform various processes with respect to a copy picture image according to the selected position.
2. Description of the Prior Art
FIG. 1 shows a main part schematic arrangement of an example of a conventional electrophotographic apparatus using the Carlson process. In FIG. 1, in copying, a photosensitive body 1 is rotated in the direction of the arrow 2. First, charges are uniformly applied to the surface of the photosensitive body 1 by corona charging from a charger 3. A document surface 5 of a document 4 is irradiated by a fluorescent lamp 6 functioning as a document irradiation means and a reflection image of the document surface 5 is focused onto the photosensitive body 1 through a focusing optical system 7 such as an optical fiber arrangement functioning as a lens, so that the document surface image is exposed successively from the right end to the left end of the document surface 5 onto the photosensitive body 1 in synchronism with the rotation of the photosensitive body 1 so as to thereby to form thereon an electrostatic latent image. A developer 8 allows toners to be adhered to the photosensitive body 1 in accordance with distribution of charges caused by the electrostatic latent image, so as to thereby to form a visible image on the photosensitive body 1. The visible image is transferred by a transfer charger 9 onto a copy sheet 10 moved in the direction of the arrow 11 in synchronism with the rotation of the photosensitive body 1 in the direction of the arrow 2 so as to form a copy picture image on the sheet 10. Here, it is known that one of primary factors which determine the density of the copy picture image is the quantity of residual charges of the electrostatic latent image and the quantity of residual charges is determined in accordance with the intensity of exposure to the photosensitive body 1.
Recently, in obtaining a copy picture image, there are such requirements that the density of the picture image would be adjusted and various processes would be performed with respect to the picture image, such that, for example, a specified portion of the picture image is erased or alternatively only the specified portion is caused to remain.
In the conventional electrophotographic apparatus, however, an exposure light source to the photosensitive body 1 is only a single fluoroscent lamp 6, and moreover light from the fluorescent lamp 6 is reflected from the document surface 5 to irradiate the photosensitive body 1, there being provided no irradiation means for directly irradiating the photosensitive body 1. Accordingly, the intensity of exposure to the photosensitive body 1 can be decreased, but, on the contrary, it is not practical to increase the intensity of exposure because the quantity of light emission of the fluorescent lamp 6 must be greatly increased. As a matter of course, if it is intended that a specified portion of the document picture image is to be erased, it is difficult to adjust the intensity of exposure for every sectioned region in accordance with a selected position. In other words, it has been difficult to perform copy picture image control.
An example of the conventional electrophotographic apparatus which can perform the copy picture image control is disclosed in U.S. Pat. No. 4,215,929 (Aug. 5, 1980) entitled IMAGE FORMING METHOD AND APPARATUS CAPABLE OF CONTROLLING AN ELECTROSTATIC IMAGE FORMATION AREA. The disclosed image forming method is performed by an arrangement constituted by a means for superimposing an original picture image exposing light and a control light, a mask member for controlling the control light, and a control means for controlling the mask member. This arrangement is complicated and expensive. Furthermore, since it is intended to obtain a desired region of the original picture image by controlling the control light by the mask member, the control by the control means becomes more complex as a shape of the desired region becomes more complicated.